Synthesis and Structure of <r-Complexes of the Chiral Rhenium Lewis Acid
[(//5-C5H 5)Re(NO)(PPh3)]+ and Aromatic Nitrogen Heterocycles
Michael A. Dewey, D. Andrew Knight, A tta M. Arif, and J. A. Gladysz*
Department o f Chemistry, University o f Utah, Salt Lake City, U tah 84112, U .S .A .
Z. Naturforsch. 47b, 1 1 7 5 -1184(1992); received December 30, 1991
Aromatic N itrogen Heterocycles, Chiral Rhenium Lewis Acid
R eactions o f (//5-C5H 5)R e(N O )(PPh3)(OTf) (1) with pyridine, quinoline, and isoquinoline
give the respective er-adducts [(^5-C5H 5)Re(NO)(PPh3)(N C ;<.Hv)]+T fO _ (2 -4 ) in 8 6 -9 5 %
yields. However, 1 and 8-m ethylquinoline do not react in refluxing xylene (16 h). Reactions o f
(+)-(i?)-l with quinoline and isoquinoline give (-)-(S)-3 and (+)-(S)-4. Both products form
with retention o f configuration at rhenium and in >98% ee, as assayed by subsequent reac­
tions with (C H 3C H 2)4N +C N - to give (+ > (5 )-(^ 5-C5H5)R e(N O )(PPh3)(CN). The crystal struc­
tures o f 3 (triclinic; P I , a = 9.879(1) A, b = 16.677(2) A, c = 9.962(1) Ä, a = 91.477(3)°,
ß = 99.155(3)°, y = 100.633(3)°, Z = 2) and 4 (triclinic, P 1, a = 10.961(2) Ä, b = 15.770(2) Ä,
c = 10.159(1) A, a = 87.65(2)°, ß = 109.88(2)°, y = 101.27(2)°, Z = 2) are determined, and the
R e - N conform ations analyzed.
Introduction
Transition metal complexes o f aromatic nitro­
gen heterocycles [1] are of considerable interest in
several contexts. First, such com pounds can serve
as reactivity models for metal-catalyzed hydrodenitrogenation (H D N ) processes [2-4], Second, nu­
m erous chiral hydroquinoline and hydroisoquinoline derivatives are im portant pharmaceutical
agents [5]. M etal-m ediated asymmetric transfor­
m ations may enable enantioselective syntheses of
these com pounds [6].
We have conducted an extensive study of com­
plexes o f unsaturated organic ligands and the chir­
al rhenium Lewis acid [(/75-C 5H 5)Re(NO)(PPh3)]+
(I). In particular, 7r-alkene [7], 7r-aldehyde [8], and
cr-ketone [9] adducts have been found to undergo
highly diastereoselective nucleophilic attack. Re­
cently, simple amine adducts o f I have been syn­
thesized [10]. We wondered if this chemistry could
be extended to unsaturated nitrogen donor ligands
such as imines and arom atic heterocycles. Thus,
we sought to prepare and characterize the neces­
sary precursor complexes.
In this paper, we report (A) high yield syntheses
o f racemic and optically active pyridine, quinoline
and isoquinoline complexes of the formula
[(^5-C5H 5)Re(N O )(PPh3)(N C vH v)]+TfO -, (B) the
* Reprint requests to Prof. J. A. Gladysz.
Verlag der Zeitschrift für Naturforschung,
D -W -7400 Tübingen
0 9 3 2 -0 7 7 6 /9 2 /0 8 0 0 - 1175/$ 01.00/0
spectroscopic characterization of these com ­
pounds, as well as crystal structures o f the quino­
line and isoquinoline complexes, and (C) facile
cyanide ion displacement of the arom atic hetero­
cycle ligands. These data provide the groundwork
for interpreting highly diastereoselective additions
described elsewhere [11]. A portion of this work
has been com municated [12].
Results
1. Synthesis and characterization o f o-heterocycle
complexes
The triflate complex (^5-C5H 5)Re(N O )(PPh3)(OTf) (1) has been previously shown to react with
primary, secondary, and tertiary amines to give
the corresponding adducts [(^5-C5H 5)Re(NO)(PPh3)(N R R 'R ")]+TfO - in high yields [10], Thus, 1
was generated in toluene as described earlier [13]
and treated with 5 equivalents of pyridine
(Scheme I). After 2 h, w orkup gave the cr-pyridine
complex [(/75-C5H 5)Re(N O )(PPh3)(N C 5H 5)]+TfCT
(2) as an analytically pure orange powder in 95%
yield.
Similar reactions with quinoline and isoqui­
noline gave the corresponding cr-complexes
[0/5-C5H 5)Re(NO)(PPh3)(NC9H 7)]+T fO “ (3, 4) in
8 6 -92% yields (Scheme I). However, the complete
formation of quinoline complex 3 required heating
for 3 h at 60 °C. Single crystals o f 3 and 4 were
readily obtained from C H 2Cl2/hexane. No reac­
tion was observed when 1 and 8-methylquinoline
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1176
M. A. Dewey et al. • Arom atic Nitrogen Heterocycles
exhibited by the “isosteric” neutral phenyl complex 0/5-C5H s)Re(NO)(PPh3)(C6H 5) (5) [14).
Quinoline, unlike pyridine, has a carbon substi­
tuent ortho to the donor nitrogen. We thought that
this increased bulk might lead to a higher
R e -N C VH Vrotational barrier in 3, thus allowing
the observation of rotam ers of the general types II
and III (Fig. 1). Hence, N M R spectra o f 3 (’H, 31P,
l3C) were recorded at - 9 0 °C in C D 2C12. Reso­
nances broadened and shifted somewhat. How­
ever, with the exception o f some PPh3 carbon reso­
nances, no decoalescence was observed. Similar
broadening, but no PPh3 carbon decoalescence,
occurred in parallel experiments with the isoquinoline complex 4.
2. Crystal structures
no reaction :
Scheme I. Reactions o f the triflate com plex (?75-C5H 5)Re(N O )(PPh3)(OTf) (1) and aromatic nitrogen heterocy­
cles.
were refluxed in toluene for 24 h, or xylene for
16 h.
Complexes 2 - 4 were characterized by m icro­
analysis (Experimental Section), and IR and
N M R ('H , 13C, 31P) spectroscopy (Table I). The IR
vN0 values (1692-1698 cm“1) and cyclopentadienyl
'H and 13C N M R resonances (Ö 5.62-5.68;
9 2 -9 3 ppm) resembled those o f the analogous
amine complexes [10]. The am bient tem perature
13C N M R spectrum o f 2 exhibited three pyridine
carbon resonances (156.3, 137.4, 126.3 ppm), in­
dicative of rapid rotation about the R e -N C 5H 5
bond on the N M R time scale. In an attem pt to decoalesce the ortho and m eta carbon resonances,
a 13C N M R spectrum was recorded at -9 0 °C in
C D 2C12. N o decoalescence or significant line
broadening was observed. Similar behavior was
X-Ray data were collected on 3 and 4 under the
conditions summarized in Table II. Refinement
(Experimental Section) yielded the structures
shown in Fig. 2. In order to facilitate the com pari­
son of metrical param eters, nearly identical atomic
numbering systems were employed. Atom ic co­
ordinates, bond lengths and angles, and torsion
angles are given in Tables III and IV.
In order to characterize the rhenium -nitrogen
bond conform ations in 3 and 4, least squares
planes were calculated for the heterocyclic ligands.
The rhenium was displaced 0.27 Ä from the arene
plane in 3, but only 0.08 Ä in 4. The R e -N O and
R e -P P h 3 bonds made angles o f 22.0° and 65.1°
with the plane in 3, and 33.6° and 55.7° in 4. As
would be expected, these values closely matched
the O N - R e - N 2 -C 3 2 and O N - R e - N 2 - C 2 4
torsion angles (3: -23.5°, 68.5°; 4: -31.6°, 54.6°).
Also, the plane of the isoquinoline ligand in 4
was roughly parallel to that o f the C 1 8 -C 2 3 PPh3
ON
III
Fig. 1. I: d-Orbital HOM O o f the pyramidal rhenium
fragment [(/75-C5H 5)R e(N O )(PPh3)]+; II and III: Possible
R e -N rotamers o f quinoline and isoquinoline com plex­
es [(//5-C5H 5)R e(N O )(PPh3)(N C 9H 7)]+T fO - (3 ,4 ).
M. A. Dewey et al. ■Aromatic Nitrogen Heterocycles
1177
Table I. Spectroscopic characterization o f aromatic nitrogen heterocycle complexes.
Complex
ON
|
o
ON
|
-N ,
IR
(cm -1, KBr)
pph3
vNO 1692 vs
TfO -
PPh3
vNO 1692 vs
TfO"
1698 vs
l3C {'H } N M R
(ppm)b
31P{'H } N M R
(ppm)c
8 .6 9 -8 .4 0 (m, 2 H o f N C 5H 5),
7 .7 2 -7 .3 1 (m, 9 H o f 3 C 6H 5,
1H o f N C 5H 5),
7 .3 0 -6 .9 3 (m, 6H o f 3 C 6H 5,
2H o f N C 5H 5),
5.62 (s, C5H 5).
C5H 5N at:
156.25 (s), 137.38 (s),
126.25 (s);
PPh3 at:
133.00 ( d , J = 10.6, o),
131.06 (s,p),
130.60 (d, J = 55.4,/),
128.92 (d , J = 10.5, w);
120.61 (q, JCF = 319.9, C F 3),
92.74 (d , / = 1.6 Hz, C5H 5).
16.0 (s)
8.93 ( d ,7 = 5.4, 1H o f N C 9H 7),
8.67 (d, J = 8.2, 1H o f N C 9H 7),
8.02 ( d , / = 8.2, 1H o f N C 9H 7),
7.92 (ddd, J = 7.9, 7.7, 1.7,
1H o f N C 9H 7),
7.82 (dd, / = 1.7, 8.1,
1H o f N C 9H 7),
7.71 (ddd, J = 0.8, 6.9, 7.5,
1H o f N C 9H 7),
7 .5 0 -7 .3 2 (m, 9 H o f 3C 6H 5),
7 .2 3 -7 .1 3 (m, 6H o f 3 C 6H 5,
1H o f N C 9H 7),
5.68 (s, C5H 5).
C9H 7N at:
165.19 (s, br),
149.20 (s), 140.01 (s),
132.42 (s), 130.52 (s),
129.76 (s), 129.59 (s),
127.86 (s), 122.72 (s);
PPh3 at:
133.19 (d, / = 10.8, o),
131.15 (s,/>),
129.43 (d, J = 5 4 .1 ,0 ,
129.06 ( d , / = 10.2, m);
120.72 (q, JCF = 320.0, C F3),
92.39 (s, C 5H 5).
'H N M R
(sy
8.90 (d, J = 0.8, 1H o f N C 9H 7),
8.50 ( d d ,7 = 6.7, 0.8,
1H o f N C 9H 7),
7 .8 5 -7 .6 5 (m ,4 H o f N C 9H 7),
7.55 (d, J = 6.7, 1H o f N C 9H 7),
7 .4 2 -7 .3 4 (m, 9 H o f 3 C 6H 5),
7 .2 9 -7 .1 8 (m, 6 H o f 3 C 6H 5),
5.64 (s, C5H 5).
C9H 7N at:
159.68 ( d , / = 2.4),
148.08 (s), 134.49 (s),
133.65 (s), 129.29 (s),
128.68 (s), 128.12 (s),
120.99 (s), 123.48 (s);
PPh3 at:
133.28 ( d , / = 10.2,o),
131.24 ( d , / = 2.5, p),
130.62 ( d , 7 = 5 6 .0 ,0 ,
129.12 ( d , / = 10.9, m);
120.99 (q ,/CF = 321.1, C F 3),
93.02 (s, C5H 5).
17.4 (s)
16.7 (s)
a At 300 M Hz at ambient probe temperature in CDC13 and referenced to internal SiM e4; all couplings are to 'H
unless noted and are in Hz; b at 75 M H z at ambient probe temperature in CDC13 and referenced to internal SiM e4; all
couplings are to 3IP unless noted and are in Hz; assignments o f resonances to phenyl carbons are made as described in
W. E. Buhro, S. Georgiou, J. M. Fernandez, A. T. Patton, C. E. Strouse, J. A. Gladysz, Organometallics 5, 956
(1986);c at 32 M Hz at ambient probe temperature in CDC13 and referenced to external H 3P 0 4.
phenyl ring (< 16.7°; Fig. 2). Distances of phenyl
carbons from the isoquinoline plane ranged from
3.0 Ä (C18) to 3.8 Ä (C21). The plane o f the
quinoline ligand in 3 was to a lesser degree aligned
with that of the C 6 -C 1 1 PPh3 phenyl ring
(< 35.6°). Distances of phenyl carbons from the
quinoline plane ranged from 3.4 Ä (C7) to 4.9 Ä
(CIO).
3. Syntheses o f optically active complexes
We next sought to establish routes to enantiomerically pure complexes. Hence, the optically ac­
tive triflate complex (+)-(/?)-1 [13] and isoquino­
line were reacted (Scheme II). W orkup gave the
optically active isoquinoline complex (+ )-(S)-4 in
74% yield, [a^f9 111 ± 2° [15]. The configuration at
rhenium, which corresponds to retention, was as-
1178
M. A. Dewey et al. ■Aromatic Nitrogen Heterocycles
Compound
Molecular formula
Molecular weight
Crystal system
Space group
Cell dimensions (16 °C)
a, A
b ,A
c, A
a , deg
ß, deg
y, deg
V, A 3
Z
dCaic’ gm/cm3 (16 °C)
d„bs>gm /cm 3 (22 °C)
Crystal dimensions, mm
Radiation, A
Data collection method
Scan speed, deg/min
Reflections measured
Range/indices (h , k , /)
Scan range
26 limit, deg
Total bkdg. time/scan time
N o. o f reflections between std.
Total unique data
Observed data, I > 3er(I)
Abs. coefficient, cm “1
min. transmission, %
max. transmission, %
N o. o f variables
G oodness o f fit
R = Y |IF 0I—IFCI |/Z |F 0|
i?w = [ S w (|F 0| - | F c|)2/S w |F 0|2]'/2
zf/<7(max.)
A q (max.), e/Ä 3
Table II. Summary o f crys­
tallography data for quinoline complex 3 and isoquinoline complex 4.
3
C33H ,7F 3N , 0 4PReS
821.8
triclinic
PI ( # 2 )
4
C33H ,7F 3N , 0 4PReS
821.8
triclinic
PI (# 2 )
9.879(1)
16.677(2)
9.962(1)
91.477(3)
99.155(3)
100.633(3)
1590.05
2
1.72
1.72
0 .3 0 x 0 .2 8 x 0 .1 8
M o K a (0.71073)
10.961(2)
15.770(2)
10.159(1)
87.65(2)
109.88(2)
101.27(2)
1619.01
2
1.69
1.68
0 .3 3 x 0 .2 3 x 0 .1 8
M oK a (0.71073)
0-26
6-26
3.0
5709
0 ,1 1 ,- 1 9 ,1 9 ,- 1 1 ,1 1
K a, —1.3 to K a 2 + 1 .6
2 .0 -4 5 .0
0.0
98
5709
4953
40.4
66.20
99.99
406
4.08
0.034
0.040
0.009
1.712, 0.84 Ä from Re
3.0
4538
0 ,1 2 ,- 1 7 ,1 7 ,- 1 0 ,1 0
K a, - 1 .3 to K a , +1.6
2 .0 -5 0 .0
0.0
97
4273
4273
39.7
81.21
99.99
406
1.20
0.021
0.024
0.001
0.492, 1.22 Ä from Re
Table III. Atomic coordinates for 3 and 4.
4
3
Atom
Re
P
Ol
N 1
N2
Cl
C2
C3
C4
C5
C6
Cl
C8
C9
CIO
C ll
C 12
C 13
C 14
X
0.15591(3)
0.0999(2)
-0.1000(6)
0.0086(6)
0.3200(5)
0.3215(9)
0.2739(8)
0.1303(8)
0.0873(9)
0.206(1)
0.1571(7)
0.1364(8)
0.185(1)
0.254(1)
0.2717(9)
0.2252(7)
0.1597(6)
0.2985(7)
0.3469(8)
y
0.33134(2)
0.1906(1)
0.3556(4)
0.3453(4)
0.3543(3)
0.3985(5)
0.3193(5)
0.3085(5)
0.3823(6)
0.4378(5)
0.1698(4)
0.2228(5)
0.2143(6)
0.1506(6)
0.0958(5)
0.1054(5)
0.1149(4)
0.1234(4)
0.0651(5)
2
0.22156(3)
0.1408(2)
0.0437(6)
0.1086(6)
0.0982(5)
0.4028(8)
0.4344(7)
0.4325(7)
0.4016(8)
0.3835(8)
-0 .0 1 9 2 (6 )
-0 .1 2 1 2 (7 )
-0 .2 4 2 5 (8 )
-0 .2 6 3 1 (8 )
-0 .1 6 3 2 (9 )
-0 .0 4 1 7 (8 )
0.2531(6)
0.3094(8)
0.3911(9)
u eq
3.230(5)
3.26(3)
6.6(1)
4.2(1)
3.5(1)
5.5(2)
4.9(2)
5.0(2)
5.9(2)
6.3(2)
3.6(1)
4.8(2)
6.3(2)
6.9(2)
5.8(2)
4.6(2)
3.5(1)
4.7(2)
5.6(2)
X
y
0.13405(2) 0.34484(1)
0.0826(1)
0.19862(7)
-0 .1 1 3 3 (4 )
0.3779(3)
-0 .0 1 1 8 (4 )
0.3644(2)
0.2533(3)
0.3829(2)
0.1468(6)
0.3043(4)
0.2792(6)
0.3269(4)
0.4147(4)
0.3050(5)
0.1924(6)
0.4500(3)
0.0928(5)
0.3797(4)
-0 .0 9 6 7 (4 )
0.1579(3)
-0 .1 6 7 3 (4 )
0.1728(3)
-0 .3 0 2 8 (4 )
0.1427(3)
-0 .3 6 8 5 (5 )
0.1002(3)
-0 .3 0 0 0 (5 )
0.0868(3)
-0 .1 6 3 3 (4 )
0.1141(3)
0.1522(4)
0.1215(3)
0.0532(3)
0.0731(5)
0.1299(5) -0 .0 0 2 5 (3 )
z
0.20664(2)
0.1248(1)
-0.0036(5)
0.0787(4)
0.0768(3)
0.4223(5)
0.4244(5)
0.3981(5)
0.3792(6)
0.3958(5)
0.0646(4)
0.1499(5)
0.1086(6)
-0.0193(7)
-0.1059(6)
-0.0636(5)
0.2557(4)
0.2963(5)
0.3986(5)
u eq
3.458(3)
3.15(2)
8.4(1)
4.8(1)
3.44(8)
6.9(2)
5.9(1)
5.5(1)
6.8(1)
7.2(1)
3.55(9)
4.6(1)
5.5(1)
6.0(1)
5.5(1)
4.4(1)
3.58(9)
4.5(1)
5.7(1)
M. A. Dewey et al. • Aromatic Nitrogen Heterocycles
1179
Table III. (Continued).
4
3
Atom
C 15
C 16
C 17
C 18
C 19
C20
C21
C22
C23
C 24
C25
C 26
C27
C28
C29
C 30
C31
C 32
y
0.2549(9)
0.1167(9)
0.0672(8)
-0.0909(6)
-0.1585(8)
-0.3035(8)
-0.3778(8)
-0.3118(8)
-0.1671(7)
0.4377(1)
0.5436(8)
0.5400(8)
0.4281(8)
0.419(1)
0.313(1)
0.210(1)
0.2129(8)
0.3200(7)
-0.0027(5)
-0.0127(5)
0.0454(5)
0.1567(4)
0.1186(5)
0.0940(5)
0.1068(5)
0.1441(5)
0.1705(5)
0.3202(4)
0.3252(5)
0.3651(5)
0.4038(4)
0.4464(5)
0.4863(5)
0.4860(5)
0.4451(4)
0.4006(4)
z
0.4189(9)
0.3646(9)
0.2828(8)
0.1043(7)
-0 .0 2 0 3 (8 )
-0 .0 4 3 (1 )
0.057(1)
0.181(1)
0.2044(8)
0.1347(8)
0.0654(9)
-0 .0 5 2 3 (9 )
-0 .0 9 6 2 (7 )
-0 .2 1 8 0 (8 )
-0 .2 5 5 7 (8 )
-0 .1 7 4 3 (9 )
-0 .0 5 6 5 (8 )
-0 .0 1 6 8 (7 )
u eq
X
y
5.8(2)
6.1(2)
5.0(2)
3.7(1)
4.8(2)
6.1(2)
6.2(2)
5.9(2)
4.8(2)
4.5(2)
5.4(2)
5.7(2)
4.6(2)
6.1(2)
6.3(2)
6.0(2)
4.9(2)
3.8(1)
0.2654(6)
0.3454(5)
0.2891(4)
0.1293(4)
0.0948(4)
0.1344(5)
0.2071(5)
0.2389(4)
0.2014(4)
0.3529(4)
0.4186(4)
0.5173(4)
0.5711(4)
0.5307(5)
0.4380(5)
0.3783(4)
0.2787(4)
0.2202(4)
0.0100(3)
0.0767(3)
0.1322(3)
0.1783(3)
0.2323(3)
0.2251(3)
0.1632(4)
0.1085(3)
0.1158(3)
0.3461(3)
0.3639(3)
0.3177(3)
0.3309(3)
0.3910(4)
0.4384(3)
0.4249(3)
0.4673(3)
0.4463(3)
z
0.4604(6)
0.4206(6)
0.3168(5)
-0 .0259(4)
-0.1 3 9 0 (4 )
-0 .2527(5)
-0.2561(5)
-0 .1468(5)
-0.0300(5)
0.0782(4)
-0.0199(4)
-0 .0203(5)
-0 .1247(5)
-0 .2299(5)
-0 .2298(5)
-0 .1243(4)
-0 .1181(5)
-0 .0201(5)
u eq
5.9(1)
5.7(1)
4.8(1)
3.36(9)
4.1(1)
5.3(1)
5.6(1)
5.4(1)
4.2(1)
3.40(9)
3.33(9)
4.2(1)
5.0(1)
5.3(1)
4.8(1)
3.7(1)
4.3(1)
4.2(1)
Anisotropically refined atoms are given in the form o f the isotropic equivalent displacement parameter defined as:
(4/3)[a2U ( l,l ) + b1U (2,2) + c2U (3,3) + oft(cosy)U (l,2) + a c(co sß )U (l,3 ) + M c o s« )U (2 ,3 )].
Fig. 2. Structures o f the cations o f quinoline complex 3 and isoquinoline com plex 4: (a) numbering diagrams; (b)
Newman-type projections down the N 2 - R e bonds.
M. A. Dewey et al. • Aromatic Nitrogen Heterocycles
1180
Table IV. Selected bond lengths (Ä), bond angles (°),
and torsion angles (°) in 3 and 4a.
R e -N 2
R e -P
R e -N l
N l-O l
R e -C l
R e -C 2
R e -C 3
R e -C 4
R e -C 5
N 2 -C 2 4
N 2 -C 3 2
C 2 4 -C 2 5
C 2 5 -C 3 0
C 2 5 -C 2 6
C 2 6 -C 2 7
C 2 7 -C 2 8
C 2 7 -C 3 2
C 2 8 -C 2 9
C 2 9 -C 3 0
C 3 0 -C 3 1
C 3 1 -C 3 2
P -C 6
P - C 12
P -C 1 8
N 2 -R e -P
N 2 -R e -N 1
P -R e -N l
R e -N l-O l
R e -N 2 -C 2 4
R e -N 2 -C 3 2
C 2 4 -N 2 -C 3 2
N 2 -C 2 4 -C 2 5
N 2 -C 3 2 -C 3 1
C 2 4 -C 2 5 -C 2 6
C 2 4 -C 2 5 -C 3 0
C 2 5 -C 2 6 -C 2 7
C 2 5 -C 3 0 -C 2 9
C 2 5 -C 3 0 -C 3 1
C 2 6 -C 2 5 -C 3 0
C 2 6 -C 2 7 -C 2 8
C 2 6 -C 2 7 -C 3 2
C 2 7 -C 2 8 -C 2 9
C 2 7 -C 3 2 -C 3 1
C 2 8 -C 2 7 -C 3 2
C 2 8 -C 2 9 -C 3 0
C 2 9 -C 3 0 -C 3 1
C 3 0 -C 3 1 -C 3 2
P -R e -N 2 -C 2 4
P -R e -N 2 -C 3 2
N l-R e -N 2 -C 2 4
N l-R e -N 2 -C 3 2
3
4
2.171(3)
2.3963(8)
1.748(3)
1.204(4)
2.339(4)
2.284(4)
2.191(4)
2.218(4)
2.296(4)
1.333(4)
1.398(4)
1.390(5)
2.147(3)
2.378(1)
1.756(4)
1.195(5)
2.223(5)
2.288(5)
2.323(4)
2.301(5)
2.230(5)
1.328(5)
1.385(5)
1.406(5)
1.417(5)
1.419(6)
1.369(6)
1.412(7)
-
1.362(6)
1.397(6)
1.421(5)
1.421(5)
1.355(7)
1.398(6)
1.371(5)
1.415(5)
1.820(3)
1.826(3)
1.839(3)
90.38(7)
102.6(1)
87.1(1)
172.5(3)
116.9(2)
126.5(2)
116.6(3)
125.2(3)
120.8(3)
118.6(4)
-
119.6(4)
-
121.9(4)
119.2(3)
121.0(4)
118.7(3)
118.9(4)
119.9(4)
121.4(4)
120.0(4)
68.5(5)
-1 1 0 .7 (5 )
155.6(5)
- 23.5(5)
signed by analogy to the results of closely related
substitution reactions [13, 16], and the commonly
observed correlation with the sign of [ a ] ^ in this
series o f com pounds [7 -9 , 13, 16].
..Ret
..Re...
ON"’ |
ON"’’ { "'PPh3
OTf
'"PPh3
TfO~
(-)-(S)-3
(CH3CH2)4N+
CN"
-
1.374(7)
1.424(6)
1.406(6)
1.355(6)
1.836(4)
1.835(4)
1.829(4)
91.65(8)
94.1(2)
90.0(1)
177.1(4)
124.0(3)
118.2(3)
117.7(3)
123.1(3)
122.7(3)
120.7(4)
118.7(4)
119.4(4)
118.7(4)
117.2(4)
120.5(4)
120.6(4)
-
121.3(4)
-
119.5(4)
124.0(4)
120.4(4)
54.6(3)
-1 2 1 .7 (3 )
144.7(3)
- 31.6(3)
a Bond lengths and angles involving the phenyl rings
have been omitted.
.
(CH3CH2)4N+CN-
..Ret
----------------------►
ON"” i "PPh3
.N .
TfO’
ON"
...Re...,
j "PPh3
CN
(+)-(S)-6
(+)-(S)-4
Scheme II. Syntheses o f optically active complexes.
Complex (+)-(S)-4 was subsequently treated
with
the cyanide
salt (CH 3CH 2)4N +CN~
(Scheme II). W orkup gave the previously charac­
terized optically active cyanide complex (+)-(£)(^5-C5H 5)Re(NO)(PPh3)(CN) ((+)-(S>6) [10] in
74% yield, [a]f|9 182 ± 2°. The optical rotation in­
dicated an enantiomeric purity of > 98% ee. N M R
analysis with (+)-Eu(hfc)3 also showed an enan­
tiomeric purity of > 9 8 % ee [10]. This in turn
bounds the enantiomeric purity of (+)-(S)-4 as
> 9 8 % ee.
Next, ( + )-(/?)-l and quinoline were reacted at
60 °C (Scheme II). W orkup gave the levorotatory
quinoline complex (-)-3 in 81% yield, [a]^9
-101 ± 2 ° [15], This contrasted with the dextrorotary substitution product obtained with isoquinoline. Thus, (~)-3 was treated with
(C H 3C H 2)4N +CN~. W orkup gave (+)-(5>6 in
71% yield, [a]||9 180 ± 8° [15]. Hence, the optically
active triflate complex (+)-(/?)-! is converted to
1181
M. A. D ew ey et al. ■Aromatic Nitrogen Heterocycles
the same enantiom er o f the cyanide complex, (+)(S)-6, regardless of whether quinoline or isoquino­
line is employed. This strongly suggests that quin­
oline and isoquinoline complexes of identical ab­
solute configurations are generated in Scheme II.
Accordingly, (~)-3 was assigned as (-)-(S)-3.
Thus, 3 is one o f three optically active [(^5C5H 5)Re(NO)(PPh3)(X)]”+ complexes found to
date (out of over one hundred) with an anom alous
sign o f [a]589. The others are the benzoyl complex
(7 5-C5H 5)Re(NO)(PPh3)(COC6H 5) and the phenylacetylene
complex
[(^5-C5H 5)Re(NO)(PPh3)(H C = C P h )]+BF4~ [17].
Discussion
To our knowledge, 3 and 4 constitute the first
pair o f structurally characterized quinoline and
isoquinoline complexes. The R e - N 2 bonds
(2.171(3), 2.147(3) Ä) are slightly shorter than that
found in the analogous dimethyl amine complex
t(l,5-C 5H 5)Re(NO)(PPh3)(H N (C H 3)2)]*TfO(7,
2.193(4) Ä) [10], and longer than that in the neu­
tral phenylamido complex (^5-C5H 5)Re(NO)(PPh3)(N H C 6H 5) (2.076(6) Ä) [18], The contraction rela­
tive to 7 may be a consequence of ligand unsatura­
tion. The rhenium fragment I is a strong n donor,
with the d orbital HOM O shown in Fig. 1 [19]. The
quinoline and isoquinoline ligands adopt R e -N
conform ations that allow a high degree of overlap
with vacant n* orbitals.
Complexes 1 - 7 are formally octahedral. Ac­
cordingly, the crystal structures of 4 and 7 exhibit
O N - R e - P , P - R e - N C , and O N - R e - N C bond
angles of 90-95°. However, the corresponding
bond angles in the quinoline complex 3 (87.1(1)°,
90.38(7)°, 102.6(1)°) show greater deviations from
90°. Also, 3 exhibits a longer R e - N 2 bond than 4,
and the rhenium is further displaced from the
plane o f the heterocycle. We suggest that this likely
reflects the presence o f a substituent ortho to the
donor nitrogen in 3, and consequential strain-induced deformations.
In principle, the heterocyclic ligands in 3, 4 can
adopt several possible conformations. The inter­
stice between the nitrosyl and bulky PPh3 ligand is
the m ost congested [20]. Thus, rotamers o f the gen­
eral types II and III (Fig. 1) are the most probable.
The interstice between the small nitrosyl and medi­
um-sized cyclopentadienyl ligand is the most spa­
cious. Accordingly, the quinoline ligand in 3
adopts a conform ation o f the type II. However,
the isoquinoline ligand in 4, which bears substi­
tuents further removed from the donor nitrogen
(m eta, para), adopts a conform ation of the type
III. This may be due in part to n interactions be­
tween the isoquinoline ligand and a PPh3 phenyl
ring. However, we suggest that in solution, rotamer II dominates. The vinyl complex ( £)-(rj 5C5H 5)Re(N O )(PPh3)(CH = C H C 6H 5) has been pre­
viously shown to adopt a R e - C conform ation of
the type III in the solid state, but one o f type II in
solution [21].
A search o f the Cam bridge Structural Database
showed that structurally characterized isoquino­
line complexes are relatively rare [22]. However,
many quinoline complexes were located [23], Sur­
prisingly, no structural studies o f free quinoline
and isoquinoline appear to have been conducted.
However, data on solvates, and theoretical investi­
gations, have been reported [24],
Only a few series o f pyridine, quinoline, and iso­
quinoline complexes involving metals in lower oxi­
dation states have been previously characterized
[25]. Examples include the rhodium (I) complexes
[(C 0D )R h(N C xH>,)2]+C104- and [Rh(CO)(PPh3)2(N C vH v)]+C104~ [25a, b], and an extensive series
of ruthenium (II) complexes [(^5-C5M e5)Ru(N C C H 3)2(N C ,H v)]+P F 6- prepared by Fish [3b,c],
In certain cases, the latter can be converted (with
acetonitrile loss) to ^-heterocycle ^-complexes.
In summary, this study has established the ready
availability o f the racemic and optically active aro­
matic nitrogen heterocycle complexes 2 - 4 , and
structural properties that will aid in the interpreta­
tion o f diastereoselective addition reactions [11].
We anticipate that metal complexes of such li­
gands, which are capable o f exhibiting a variety of
binding modes [3 a -c , 6b, 26], will be the focus of
considerable reactivity studies in the near future
[6c].
Experimental Section
General data
Experimental procedures, acquisition o f re­
agents and purification o f solvents were identical
to those given in a previous paper [10] with the
M. A. Dewey et al. ■Aromatic Nitrogen Heterocycles
1182
following additions: pyridine, quinoline, and isoquinoline (Aldrich), distilled from zinc dust;
8-methylquinoline (Fluka), vacuum distilled.
[ ( rj--C5H 5)R e (N O ) ( PPh 3) ( N C 5H 5) ] +TfO~ (2)
A Schlenk flask was charged with (^5-C5H 5)Re(NO)(PPh3)(CH 3) (10 [27], 0.245 g, 0.439 mmol),
toluene (15 ml), and a stir bar and cooled to
-4 5 °C (C H 3CN/liquid N 2 bath). Then H O Tf
(0.0389 ml, 0.439 mmol) was added with stirring to
generate (>75-C5H 5)Re(NO)(PPh3)(OTf) (1) [13].
After 5 min, pyridine (0.178 ml, 2.20 mmol) was
added with stirring. The bath was removed and the
mixture allowed to warm to room tem perature.
Some product precipitated. After 2 h, hexane
(50 ml) was added with stirring to complete precip­
itation. The resulting orange powder was collected
by filtration, washed with hexane and dried under
oil pump vacuum to give 2 (0.321 g, 0.417 mmol,
95%), m .p. 223-225 °C dec.
Analysis fo r C 29H 25F3N ^04P R eS
Calcd C 45.13
Found C 45.01
H 3.27,
H 3.22.
[ (rf-C 5H 5)R e (N O ) ( PPh3) ( N C 9H 7) ] +TfO~ (3)
Complex 10 (0.928 g, 1.66 mmol), toluene
(30 ml), H O Tf (0.147 ml, 1.66 mmol), and quino­
line (0.982 ml, 8.30 mmol) were combined in a pro­
cedure analogous to that given for 2. The flask was
immersed in a 60 °C oil bath. After 3 h, the bath
was removed and the mixture was allowed to cool
to room temperature. Some product precipitated.
After lh , hexane (150 ml) was added to complete
precipitation. The resulting orange powder was
collected as above to give 3 (1.165 g, 1.43 mmol,
86%), m. p. 230-231 °C dec.
Analysis fo r C 33H v F3N 20 4P R eS
Calcd C 48.23
Found C 48.17
H 3.31,
H 3.35.
[ (rj5-C 5H 5)R e (N O ) (PPh 3)(iso -N C 9H 7) J +TfO~ (4)
Complex 10 (1.002 g, 1.794 mmol), toluene
(25 ml), H O Tf (0.159 ml, 1.79 mmol), and isoquinoline (1.060 ml, 8.970 mmol) were combined
in a procedure analogous to that given for 2. An
identical workup gave 4 as an orange powder
(1.352 g, 1.650 mmol, 92%), m .p. 216-218 °C
dec.
Analysis fo r C 33H v F3N 10 4P R eS
Calcd C 48.23
Found C 48.14
H 3.31,
H 3.31.
( - ) - ( S )-3
Complex ( + )-(S>10 (0.159 g, 0.285 mmol) [27],
toluene (5 ml), H O Tf (0.0252 ml, 0.285 mmol),
and quinoline (0.169 ml, 1.43 mmol) were com ­
bined to generate ( + )-(/?)-1 in a procedure analo­
gous to that given for 3. A brown oil formed when
the reaction mixture was cooled. After 12 h, sol­
vent was removed under oil pump vacuum. The re­
sulting residue was extracted with C H 2Cl2/hexane
(30 ml, 2:1 v/v). The solution was slowly concen­
trated until a solid formed and the supernatant
was nearly colorless. The resulting orange powder
was collected as above to give (-)-(S )-3 (0.191 g,
0.231 mmol, 81%), m .p. 107-110 °C dec, [a]^f9
-101 ± 2 ° (c 0.864 mg/ml) [15b],
Analysis fo r C 33H v F3N-,04PReS
Calcd C 48.23
Found C 48.12
H 3.31,
H3.41.
( + )-(S )-4
Complex (+)-(S)-10 (0.180 g, 0.322 mmol), to ­
luene (7 ml), H O Tf (0.285 ml, 0.322 mmol), and
isoquinoline (0.190 ml, 1.61 mmol) were combined
in a procedure analogous to that given for 4. Hex­
ane addition gave an oil. Solvent was then re­
moved under oil pum p vacuum. The resulting resi­
due was triturated in ether (50 ml) until a fine or­
ange powder formed. This was collected as above
to give (+)-(S)-4 (0.196 g, 0.238 mmol, 74%), m .p.
200-202 °C dec, [«]||9 111 ± 2° (c 0.948 mg/ml
[15b].
Analysis fo r C 33H v F3N 10 4PR eS
Calcd C 48.23
Found C 48.00
H 3.31,
H 3.29.
Reaction o f ( - ) - ( S )-3 and (C H 3CH 2) 4N +CN~
A Schlenk flask was charged with ( - ) - ( S )-3
(0.079 g, 0.097 mmol), CH,C1, (5 ml), and a stir
bar. Then (CH 3C H 2)fN +CN - (0.018 g, 0.12 mmol)
was added with stirring. After 5 min, hexane
(25 ml) was slowly added with stirring. An oil
formed, and the solvent was removed under oil
pum p vacuum. The resulting residue was triturat­
ed in ether (10 ml) until a yellow powder formed.
This was collected by filtration and chrom ato­
graphed on a 2 cm silica gel column in TH F. Sol­
vent was removed from a yellow band to give
(+)-(S )-(^-C 5H 5)Re(NO)(PPh3)(CN)
((+)-(S>6)
[10]; 0.039 g, 0.69 mmol, 71%), [«]&, 180±8°
(c 0.940 mg/ml) [15 b]. Optical purity: [a], > 95% ee;
( + )-Eu(hfc)3, > 9 8 % ee [10].
M. A. Dewey et al. ■Aromatic Nitrogen Heterocycles
Reaction o f ( + ) - ( S ) - 4 and ( C H 3C H 2) 4N +CN~
Complex (+)-(S>4 (0.117g, 0.143 mmol),
C H 2C12 (5 ml), and (CH3C H 2)4N +C N - (0.027 g,
0.172 mmol) were combined in a procedure analo­
gous to that given for reaction of (-)-(S)-3. An
identical workup gave (+)-(S)-6 as a yellow pow­
der (0.060 g, 0.106 mmol, 74%), [<*]52859 182 ± 2 °
( c l . 16 mg/ml) [15b]. Optical purity:
[a],
> 98 % ee; (+ )-Eu(hfc)3, > 98 % ee [ 10].
C r y sta l structures
1183
no decay during data collection. Lorentz, polariza­
tion, and empirical absorption (y/ scans) correc­
tions were applied. The structures were solved by
standard heavy-atom techniques with the SDP/
VAX package [28]. Non-hydrogen atoms were re­
fined with anisotropic therm al parameters. H ydro­
gen atom positions were calculated and added to
the structure factor calculations, but were not re­
fined. Scattering factors, and A i ' and A i " values,
were taken from the literature [29], Additional de­
tails are given elsewhere [lib ].
We thank the N IH for support of this research.
Complexes 3 , 4 were dissolved in CH 2C12 and
slowly layered with hexane. Orange prisms
formed, and were collected by filtration and dried
under a nitrogen stream. X-Ray data were collect­
ed as summarized in Table II. Cell constants
were obtained from 25 reflections in the range
20° < 2 6 < 34° (3) or 20 reflections in the range
20 < 2 6 < 28° (4). Standard reflections showed
Further details may be obtained from: Fachinformationszentrum Karlsruhe, Gesellschaft für wissenschaft­
lich-technische Information mbH, D-W -7514 Eggenstein-Leopoldshafen 2, by quoting the Registry-No.
CSD 56150, the names o f the authors and the journal ci­
tation.
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which the cyclopentadienyl ligand is considered to
be pseudoatom o f atom ic number 30. This gives the
priority sequence >75-C5H 5 > PPh3 > O T f > N O >
N C 9H 7 > C N. See K. Stanley and M. C. Baird, J.
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[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
1184
cells with c (Experimental Section) optimized for
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